1. Field of the Invention
The present invention relates to an ink composition excellent in blackness and an ink jet recording method using the same.
2. Background Art
A black ink is an important ink composition used as an ink jet recording ink composition for both monocolor and full color printings.
C.I. Food Black 2 (Japanese Patent Laid-Open No. 93766/1984) and dyes having structures analogous thereto (Japanese Patent Laid-Open No. 91577/1991) have been widely used as dyes for the black ink.
These dyes, however, have a somewhat bluish hue that is more or less different from pure black (a black color perceived, for example, from Chinese ink (sumi) or Japanese lacquer (urushi)).
For this reason, a proposal has been made on the use of a combination of these dyes with other dyes for the purpose of improving the hue (Japanese Patent Laid-Open No. 36279/1990). However, it has been found that the combination of dyes deteriorates the storage stability of the ink. Furthermore, the use of such an ink in ink jet printers, which effect printing at a high density of 300 dpi or more and a high frequency of 5 kHz or more, often gives rise to lack of jetting stability and clogging of nozzles. A special recording material (for example, coat paper comprising a substrate sheet, such as paper, an ink receiving layer containing a pigment and binder) has been proposed for the purpose of enhancing the image quality. Although the coat paper can provide pure black, it is desired that blackness and sharpness of an image will be also performed on plain paper.
In a water-base ink using a water-soluble dye, a general problem is to improve the water resistance of the print (for example, Japanese Patent Laid-Open Nos. 91577/1991, 226175/1992 and 233975/1992). The ink composition described in these Japanese Patent Laid-Open No. 36279/1990 also leaves room for an improvement in the water resistance of the print.
Additional properties which are generally required of ink compositions for an ink jet recording method are that the ink does not clog jetting nozzles, printing can be quickly resumed even though clogging occurred, and ink properties remain unchanged during storage. Therefore, the ink compositions for ink jet recording should satisfy requirements of freedom from clogging of nozzles, quick resumption of printing after clogging of nozzles and excellent storage stability in addition to pure black color and water resistance.